To Bake, or not to Bake
Is Baking necessary every time?


No.

To explain, there are some times, when it is just more of a hassle then it is worth.  For instance, when using the Blender Internal engine, which can be pretty fast, you can be using basic enough materials that by the time you finished baking, you could have finished rendering.

Regarding animation rendering and video games, that depends as well.  Non-moving lights and objects will benefit from baking, as they do not move, but the camera moves.  In videos games, the player is typically moving around the scene, which prevents lighting from being baked onto the model, as it needs to be dynamic.

About the 14 different baking modes, each one will obviously do something different, otherwise it would be one big button that says "Bake".  The other modes are important for each specific task.  For instance, baking colors, or textures, while they seem similar, using them incorrectly will most likely take a lot of time, and not produce the result you are looking for.

I am pretty sure that there are other locations you can bake from, I think at one point (stretching back here) I had a scene where I just wanted to bake a shadow for one object, so I did.  I believe you select the image you are baking, and select the object, and then you click bake, and it will bake for that one object.  I think I followed Blender Guru's tutorial here.